Hydraena pantanalensis, Perkins, Philip D., 2011

Perkins, Philip D., 2011, New records and description of fifty-four new species of aquatic beetles in the genus Hydraena Kugelann from South America (Coleoptera: Hydraenidae), Zootaxa 3074, pp. 1-198 : 46-47

Hydraena pantanalensis , new species

Figs. 85 (habitus), 89 (aedeagus), 200 (map)

Type Material. Holotype (male): Brazil: Matto Grosso, Rio Bento Gomes (Pantanal); Quelle, Quellbach, Campo Allegre, II, 15° 45' S, 56° 33' W, 1 i 1993 – 30 xii 1994, E. Stuhr. Deposited in the NMW.

Differential Diagnosis. This species has rather large and dense elytral punctures, the interstices only 0.5–1xpd on the basal 1/3; the elytra are rather convex at the summit of the posterior declivity. Similar in dorsal habitus to H. tucumanica and H. diffusa ( Figs. 74 , 85 , 139 ); differing from both species by the smaller size (ca. 1.22 mm). The aedeagus has some resemblance in basic shape to that of H. orcula . Reliable determinations will require examination of the very dissimilar male genitalia of the four species ( Figs. 78, 84–85 , 141).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.22/0.49; head 0.19/0.31; pronotum 0.29/0.39, PA 0.33, PB 0.36; elytra 0.74/0.49. The holotype is teneral; following is a prediction of the mature color. Dorsum of head piceous; pronotum testaceous in front of and behind piceous macula, ratios of color bands, as measured in midline, ca. 5/10/5; elytra dark brown; legs brown; maxillary palpi testaceous, tip not darker.

Frons punctures ca. 1–2xef, larger and denser near eyes than medially; interstices 0.5–1xpd, microreticulate, dull laterally, 1–3xpd and shining medially. Clypeus microreticulate laterally, very finely sparsely punctulate medially. Mentum microreticulate, dull, very sparsely very finely punctulate; postmentum dull, very finely densely micropunctulate. Genae concave and dull laterally, raised and weakly shining medially, without posterior ridge.

Pronotum weakly arcuate laterally; anterior margin straight behind eyes, emarginate behind frons, scintilla absent; punctures on disc slightly larger and deeper than those of frons, interstices shining, 1–3xpd, punctures larger and denser at anterior and posterior; PF1 absent; PF2 very shallow; PF3 deep; PF4 absent.

Elytra weakly arcuate laterally; summit of posterior declivity at ca. posterior 1/3; lateral explanate margins narrow; on basal 1/3 punctures slightly larger than largest pronotal punctures, punctures becoming finer and more widely spaced toward posterior. Intervals not raised, shining, on basal 1/3 ca. 0.5–1xpd, as are interstices between punctures of a row, a few punctures subserial. Apices in dorsal aspect conjointly rounded, in posterior aspect margins forming very shallow angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 1.5/1.5/5/3. P1 laminate; median carina sinuate in profile. P2 l/w ca. 2.5/1, sides slightly converging toward blunt apex, apex raised slightly above mesoventral intercoxal process. Plaques moderately wide, straight, parallel or slightly converging toward one another anteriorly, weakly raised, located at sides of deep median depression. Metaventrite with very small point on each side, extended posteriorly from margin of each mesocoxal cavity. AIS width at straight posterior margin ca. 2x P2. All tibiae slender, straight. Abdominal apex symmetrical; last tergite concave on each side of median longitudinal ridge, free margin sharply rounded. Female not yet known.

Etymology. Named in reference to the geographical distribution.

Distribution. Currently known only from the type locality ( Fig. 200).

Notes. The holotype has a very narrow transverse groove across the posterior margin of the frons ( Fig. 85 ); more specimens are needed to verify if this is constant in the species, or a variable character.

Figures

FIGURE 74. Hydraena tucumanica, holotype, dorsal and lateral habitus, and venter.

FIGURE 84. Hydraena orcula, holotype, dorsal and lateral habitus, and venter.

FIGURE 85. Hydraena pantanalensis, holotype, dorsal and lateral habitus, and venter.

FIGURE 139. Hydraena diffusa, holotype, dorsal and lateral habitus, and venter.